This invention relates to charging circuits for use in a variety of portable devices, and more particularly to a charging circuit with a fast transient input current path.
Portable electronic devices such as laptop computers, cell phones, pagers, personal digital assistants, and the like are becoming a more common tool in today""s society as the capabilities and uses of such devices continues to expand. Many portable electronic devices now include rechargeable batteries such as lithium, nickel-cadmium, or nickel-metal hydride batteries.
Some portable electronic devices may have integral charging circuits so that the battery may be recharged without removing the battery from the device. For instance, when the portable device is coupled to a power source, e.g., an AC/DC adapter providing a DC output voltage from a conventional 120 volt AC wall outlet, the charging circuit provides power to charge the battery.
The charging circuit may be further provided with a power allocation feature. In general, this power allocation feature serves to better utilize the power from a power source by varying the power provided to recharge the battery inversely with the power requirements for the rest of the portable device""s system such that the sum of the two is within some maximum predetermined tolerance limits of the power source. For instance, with a constant voltage power source, the charging current level for the battery may be varied inversely with the current level required for the balance of the portable device""s system to keep the sum within a predetermined maximum level of supply current from the power source. As such, unnecessary tripping of the power source should normally be prevented.
Such a power allocation feature typically has an input current path responsive to a sensed signal representative of the current provided by the power supply, a charging current path responsive to a sensed signal representative of the charging current provided to the portable device""s battery, and a charging voltage path responsive to a sensed signal representative of the charging voltage provided to the portable device""s battery.
However, the response time for the input current path and the charging current path is typically the same. Hence, the charging circuit is susceptible to transient conditions that may cause unintended tripping of the local power source. As fast load changes caused by high speed logic and microprocessors have increased, these transient conditions have also increased. For instance, the charging circuit may not be fast enough to decrease the charging current level to the battery in order to keep the local power source within a predetermined maximum parameter, e.g., current rating. Accordingly, there is a need in the art for a charging circuit with a power allocation feature having a fast transient input current loop.
A charging circuit consistent with the invention includes: a first path configured to accept a signal representative of at least one supply parameter from an associated power source and provide a first control signal; a second path configured to accept the signal representative of the at least one supply parameter and provide a second control signal, wherein the second path has a faster transient response time than the first input path; a third path configured to accept a signal representative of at least one charging parameter from an associated battery and provide a third control signal; and a regulating circuit configured to accept the first, second, and third control signals and regulate the at least one charging parameter for the associated battery depending on at least one of the first, second, or third control signals.
A charging circuit system consistent with the invention includes: a power source having at least one predetermined supply parameter with a predetermined maximum rating; a battery; a sensor configured to sense the at least one predetermined supply parameter and provide a sense signal representative of the at least one parameter; and a charging circuit including: a first path configured to accept the sense signal and provide a first control signal; a second path configured to accept the sense signal and provide a second control signal, wherein the second path is configured to have a faster transient response time than the first path; and a third path configured to accept a signal representative of at least one charging parameter from the battery and provide a third control signal; and a regulating circuit configured to accept the first, second, and third control signals and regulate the at least one charging parameter for the battery depending on at least one of the first, second, or third control signals.
A laptop consistent with the invention includes: a CPU; a battery; and charging circuit including: a first path configured to accept a signal representative of at least one supply parameter from an associated power source and provide a first control signal; a second path configured to accept the signal representative of the at least one supply parameter and provide a second control signal, wherein the second path has a faster transient response time than the first input path; third path configured to accept a signal representative of at least one charging parameter from an associated battery and provide a third control signal; and a regulating circuit configured to accept the first, second, and third control signals and regulate the at least one charging parameter for the associated battery depending on at least one of the first, second, or third control signals.
A method of allocating power from a power source configured to charge a battery consistent with the invention includes the steps of: sensing at least one predetermined supply parameter from the power source; providing a first control signal after a first time interval based on the sensing; providing a second control signal after a second time interval based on the sensing, wherein the second time interval is less than the first time interval; and regulating power to the battery based on at least one of the first and second control signals.